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Originally posted by w30olds
If you take the outside temp and add 30 degrees then this should give you a "target pressure" of what your high side pressure should be running around. Low side pressure should be relevent to the high on the pressure/temp chart.

Oh, now that sounds like e-bay advice there.

"Prehistoric, outdated rule of thumb" I'm selling this rule of thumb because I no longer use it. I found out recently that it only applied to systems with cap tubes and low efficiency systems but figured some of you beginners might want an easy way to hack into the HVAC market. Beginning Bid.... $0.49

Originally posted by morepwr hello ..im trying to fix my ac unit..i bought the house new ten years ago and it came with a bdp air conditioner the house is 1900 sq feet..im not sure of the tons.. i get 60 to 63 deg out of the registers..but upstares stays hot the lowest i can get it to is 85 deg in the afternoon and if i run the unit all day it will cool down to 80 at 11.30 pm..yersterday i measured the outside temp and it was 110 deg.. the temp at the ac fan was 120 deg.. i used a set of old manifold gages and the low side read 110psi and the hi side when you first start the unit peg the gage over 500psi.. then droped down to 495.. can my ac be overcharged.. what psi should i be looking for ..the ac modle number is 561aj048-f thanks for your help.. bye

With this high of head pressure you would be wise to call a service company before you loose a compressor.
Things you can do.

1. Check your filter and if it is clean, over a month old replace it.
2. Turn your system off tonight,say about 7:30pm and clean your outdoor unit,hook up spray nozzle and wash out unit holding nozzle about 10" away from outdoor coil section spraying water from top to bottom, all the way around your unit and then do it again. turn you system back on and see if this helps..

If not then better get help quickly before your compressor blows.The unit sounds like maybe restriction or bad condenser motor..

Originally posted by w30olds
If you take the outside temp and add 30 degrees then this should give you a "target pressure" of what your high side pressure should be running around. Low side pressure should be relevent to the high on the pressure/temp chart.

Oh, now that sounds like e-bay advice there.

"Prehistoric, outdated rule of thumb" I'm selling this rule of thumb because I no longer use it. I found out recently that it only applied to systems with cap tubes and low efficiency systems but figured some of you beginners might want an easy way to hack into the HVAC market. Beginning Bid.... $0.49

Ok expert what's your advice? I could tell him to check the superheat, or is that "Prehistoric, outdated rule of thumb" as well? Was just trying to give the guy an idea of where his pressures should be running.